Internal combustion engine



May 6, 1941. E MACK 2,241,211

INTERNAL COMBUST ION ENGINE Fil ed Dec. 27, 1958 Parr EMack Patented May 6, 1941 INTERNAL COMBUSTION ENGINE Perry E. Mack, Milwaukee, Wis., assignor t Briggs & .Stratton Corporation,

Milwaukee,

Wis., a corporation of Delaware Application December ,27, 1938, Serial No. 247,858

,4 Claims. (01. 184-6) This invention relates to internal combustion engines, and has particular application to small single cylinder engines of the portable type.

In engines of this type, lubrication is by the splash system and as the crankcase which contains the supply of lubricant is subject to pressure pulsations, the prevention of lubricant expulsion through bearings which form openings through the wall of the crankcase presents a serious problem.

The bearings in which the guides of the cam followers or tappets reciprocate especially pre-' sent a problem as an excessive oil spray or a large amount of oil in the valve spring chamber is apt to cause gumming and sticking of the valves.

Heretofore, diificulty has been experienced in preventing an excessive accumulation of oil at this point, and it is therefore an object of this invention to provide means whereby this objective can be achieved.

More specifically, it is an object of this invention to provide means for draining oil from the outer end of the bore through which the tappet or guide of the cam follower reciprocates.

With the above and other objects in view which will appear as the description .proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise'embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of the invention constructed in accordance with the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view showing part of a single cylinder internal combustion engine, with parts broken away and in section, to illustrate the application of this invention thereto;

Figure 2 is an enlarged sectional view taken through Figure 1 on the plane of the line 22; and

Figure 3 is a detail View of the valve for controlling the oil drain passage.

Referring now particularly to the accompanying drawing in which like numerals indicate like parts, the numeral designates the crankcase of a conventional single cylinder internal combustion engine, which, as is customary, contains asupply of lubricant. The lubricant, during operation of the engine, is splashed about to lubricate all of the moving parts accessible from the interior of the crankcase.

Among the parts lubricated in this manner are the tappets or guides 6 of the cam followers 1. These tappets or guides reciprocate in bores 8 through a wall 9 of the crankcase. The upper ends of the tappets or guides project into a valve spring chamber Hi where they abut the lower ends of the valve stems H, in the customary manner.

Inasmuch as the crankcase is subject to pressure pulsations by virtue of the reciprocation of the engine piston, it follows that lubricant which accumulates in the clearance between the bores 8 and the guides which slide therein is apt to be expelled upwardly into the valve spring chamber Hi. This is objectionable not only because of the loss of lubricant occasioned thereby, but also because the accumulation of an excessive amount of lubricant in the valve spring chamber is apt to cause gumming and sticking of the valves.

It is thus desirable to prevent this expulsion of lubricant from the outer ends of the bores 8, and to this end, these bores connect with a transverse bore l2 drilled into the wall 9 of the crankcase. The outer end of this bore is closed by a suitable plug l3, but between the bores 8, it connects with a downwardly directed bore M which opens to the interior of the crankcase to drain off the lubricant as it accumulates in the bore [2.

The lower end of the bore i4 is tapped and has a valve plug l5 threaded therein. The valve plug has a bore I6 longitudinally therethrough with its lower end opening to a counterbore IT. The peripheral edge of the bore 16, where it opens to the counterbore IT, is raised as an annular rim to form a valve seat l8 with which a disc or flap valve I 9 engages. A pin 20 holds the valve I9 in position.

With this construction, it will be readily apparent that whenever a pressure condition exists inside the crankcase, the valve I9 is held against its seat closing ofi communication between the crankcase interior and the bore I2, but whenever a subpressure obtains inside the crankcase, the valve I9 is off its seat and any lubricant in the bore 12 and excess lubricant at the upper ends of the bores 8 is drawn back into the crankcase.

From the foregoing description taken in connection with the accompanying drawing, it will be readily apparent that this invention provides an exceedingly simple and practical manner of preventing the expulsion of lubricant from the crankcase of an internal combustion engine through the bores in which the tappets or guides of the cam followers reciprocate.

What I claim as my invention is:

1. In combination: a substantially closed chamber adapted to contain a lubricant and subject to pressure pulsations: one wall of the chamber having a bore therethrough; a part movable in said bore; free motion of said part being assured by the provision of lubricant from the chamber, said wall of the chamber having another bore substantially lateral to the first named bore and opening to said first named bore near its outer end, said wall also having a tapped hole opening to said lateral bore; and a plug having a valve mounted therein threaded in said tapped hole, the valve of said plug being biased to open position and being closed only when a plenum obtains inside the chamber.

2. In combination with the crankcase of a single cylinder internal combustion engine wherein well defined pressure pulsations occur due to I the reciprocation of the engine piston: one wall of the crankcase having an opening therethrough to receive the guide of a cam follower for reciprocation therein, free motion of the cam follower in said opening being assured by lubricant derived from the crankcase; and means for preventing pressure within the crankcase from forcing lubricant out through the opening com- 3. In combination with the crankcase of a single cylinder internal combustion engine wherein well defined pressure pulsations occur due to the reciprocation of the engine piston: one wall of the crankcase having an opening therethrough forming a guideway; a member slidable in said guideway and projecting from opposite ends of the guideway, free motion of said member in the guideway being assured by lubricant derived from the crankcase; and means for preventing the expulsion of such lubricant through said guideway past the slidable member comprising, a transverse bore in said wall connecting. with the guideway near its outer end; and means for connecting'the transverse bore with the interior of the crankcase including, a valve biased to open position to thereby connect the transverse bore with the interior of the crankcase, said valve being closed by each pressure pulsation within the crankcase.

4. In combination with the crankcase of a single cylinder internal combustion engine wherein well defined pressure pulsations occur due tothe reciprocation of the engine piston: one wall of the crankcase having an opening therethrough in which the guide of a cam follower reciprocates, free motion of the cam follower in said opening being assured by lubricant derived from the crankcase; and means for preventing the expulsion of lubricant through the wall of the crankcase around the cam follower guide by the positive pressure pulsations inside the crankcase comprising, a lateral bore in the wall of the crankcase connecting with the first named opening medially of its ends; means for connecting said lateral bore with the interior of the crankcase; and a valve to close said last named means, said valve beingbiased to an open position connecting the lateral bore with the interior of the crankcase and being closed in response to the positive'pressure pulsations inside the crankcase to prevent such pulsations from forcing lubricant out of said opening.

PERRY E. MACK. p 

